(1) Field of the Invention
The present invention relates to a distributed processing system and a network monitoring system, and more particularly, to a distributed processing system for performing distributed processing to provide services and to a network monitoring system for performing distributed processing to monitor a network.
(2) Description of the Related Art
In recent years, distributed processing technique typified by a client/server model is widely used as one form of processing by a computer system. Distributed processing denotes processing wherein a plurality of computers or applications are interconnected in a networked environment, share resources and cooperatively operate to provide services.
FIG. 8 shows an example of a distributed processing system. The system shown in FIG. 8 comprises client applications 201 and 202, service applications 301 to 303, and a server application 400.
The client applications 201 and 202 are each an application which requests service information. The server application 400 is an application which collectively stores and manages the service information.
The service applications 301 to 303 are each an application which receives the service information from the server application 400 and provides the requested service information to the client applications 201 and 202.
Let it be assumed that the system shown in FIG. 8 is a system for monitoring a network. It is also assumed that the client application 201 is a GUI (Graphical User Interface) for displaying on screen information about a fault occurring on the network, and that the service application 301 is an application for providing such fault information.
The operation will be now described.
[S100] The server application 400 receives and stores fault information transmitted from the network.
[S101] The client application 201 transmits a user authentication request to the server application 400.
[S102] On recognizing authenticity of the user, the server application 400 returns a normal response to the client application 201.
[S103] The server application 400 transmits the fault information to the service application 301.
[S104] The service application 301 returns a normal response to the server application 400.
[S105] The client application 201 starts the service application 301 from which the fault information is to be notified.
[S106] The service application 301 transmits the fault information to the client application 201.
[S107] The client application 201 receives the fault information transmitted from the service application 301 and displays the information on screen.
Among the above steps, Steps S101 and S105 are executed as part of a logon operation by the client application 201. At the time of logoff, the client application 201 terminates the service application 301 and ends the use status.
In the conventional distributed processing system described above, however, when the client application 201 logs on or off, it is necessary that interrelation with the corresponding service application 301 be established before the client application 201 starts or terminates.
Specifically, the client application 201, which displays (or stops displaying) the fault information, is required to select the corresponding service application 301 before started (or terminated). Thus, the logon/logoff process performed on the part of the user involves many steps, giving rise to a problem of low efficiency.
Also, in the conventional system, in cases where the client application 201 undergoes an abnormal end and is restarted, a problem arises in that status inconsistency occurs between the client application 201 and the server application 400.
FIGS. 9(A) and 9(B) illustrate such status inconsistency between the client application 201 and the server application 400, wherein FIG. 9(A) shows normal operation and FIG. 9(B) shows a case where the client application 201 is restarted after abnormal end. In FIGS. 9(A) and 9(B), “ON” indicates logged-on state and “OFF” indicates logged-off state.
As shown in FIG. 9(A), in the case where the client application 201 has normally ended and thus is OFF, the server application 400 also is OFF. When the client application 201 is set ON, the server application 400 is instructed to log on and thus is set ON.
In the case where, as shown in FIG. 9(B), the client application 201 undergoes an abnormal end and turns OFF, the server application 400 remains ON. When the client application 201 is thereafter restarted and set ON, the server application 400 is instructed to log on; however, since the server application 400 is already ON, there is the possibility that an error arises.
Thus, in cases where the client application 201 is restarted after abnormal end, a disadvantage arises in that the server application 400, which remains in the logged-on state, is additionally instructed to log on, and this lowers the reliability of the system.